In the era of President Donald Trump, Democrats think presidents should be impeached over policy differences.

In Trump's case, the Democrats accuse him of winning the election by "colluding" with Russia to win. After nearly a year of investigations, there does not appear to be any evidence. Yet many Democrats have already called for impeachment.

In truth, Democrats want this President out because they don't like him or his policies. One of Trump's major campaign promises was to build a "wall" to protect our southern border. Never mind that, in 2006, 26 Democratic senators — including Hillary Clinton, then-Sen. Barack Obama and Chuck Schumer — voted for hundreds of miles of barriers and fencing. And every Senate Democrat voted for 2013's Border Security, Economic Opportunity, and Immigration Modernization Act, which again called for hundreds of miles of barriers.

But Trump is "racist" and "xenophobic." Rep. Al Green, D-Texas, calls Trump a "bigot in the White House who incites hatred and hostility," which, says Green, is a "high misdemeanor" that constitutes an impeachable offense.

All right, let's apply the Democrats' new standard for impeachment to President Obama and his decision in 2011 to pull all the troops from Iraq against the advice of his national security team. President George W. Bush warned his successor. Bush turned around the Iraq War with his controversial "surge," a troop increase of about 21,500 in 2007. Former Vice President Dick Cheney, in October 2011, two months before Obama pulled out all the troops in Iraq, said that Bush's 2007 agreement envisioned a negotiation for a stay-behind force: "There was another provision in (Bush's status-of-forces agreement) that's very important, seems to have been ignored, which was that we would also reserve the right to negotiate with the Iraqis on some stay-behind forces. ... They're a new democracy; they're not very well-organized yet. I worry that in the rush for the exit here, that we may in fact make it very difficult for them to succeed."

But then-Sen. Barack Obama, who called the Iraq War "dumb," not only opposed Bush's surge but also predicted it would make things worse: "I am not persuaded that 20,000 additional troops in Iraq is going to solve the sectarian violence there. In fact, I think it will do the reverse. ... So I am going to actively oppose the President's proposal."

But the surge did work.

By 2008, the violence subsided to the point where American soldiers, celebrating with Iraqis in Ramadi, were on the streets not even wearing their helmets. War correspondent Dexter Filkins, who had all but given up in Iraq when he was last there just two years earlier, could not believe the improvement: "The progress here is remarkable," said Filkins in 2008. "I came back to Iraq after being away for nearly two years, and honestly, parts of it are difficult for me to recognize. The park out in front of the house where I live — on the Tigris River — was a dead, dying, spooky place. It's now filled with people — families with children, women walking alone, even at night. That was inconceivable in 2006. The Iraqis who are out there walking in the parks were making their own judgments — that it is safe enough for them to go out for a walk. They're voting with their feet. It's a wonderful thing to see."

But Filkins warned that the gains could erode. "It's pretty clear," Filkins said, "that the calm is very fragile. The calm is built on a series of arrangements that are not self-sustaining; indeed, some of which, like the Sunni Awakening, are showing signs of coming apart. So the genie is back in the bottle, but I'm not sure for how long."

Obama, however, pulled out all the troops against the advice given by Obama's CIA chief, his secretary of defense, the United States ambassador to Iraq, his national security adviser, the Joint Chiefs of Staff and then-Secretary of State Hillary Clinton. This commander in chief with no military experience rejected the apparent unanimous advice from his defense team: Leave a stay-behind force or run the risk of terrorists filling the power vacuum.

But Obama did not listen.

As to the Joint Chiefs' opposition to what became known as the "Iraq bug-out," now-retired Army Chief of Staff Gen. Ray Odierno said: "I go back to the work we did in 2007 (through) 2010, and we got into a place that was really good. Violence was low, the economy was growing, politics looked like it was heading in the right direction. ... We thought we had it going exactly in the right direction, but now we watch it fall apart. It's frustrating. ... I think, maybe, if we had stayed a little more engaged, I think maybe it might have prevented it."

If policy disagreement is the new standard for impeachment in the Trump era, wouldn't Obama's Iraq bug-out qualify?